AIG1,The deduced 238-amino acid protein has a calculated molecular mass of 27 kD and contains 5 predicted membrane-spanning domains. AIG1 and Far17a share 37% amino acid homology. RT-PCR detected an AIG1 variant that lacks nucleotides 169 to 324, resulting in an in-frame deletion of 52 amino acids, including a membrane-spanning domain. Northern blot analysis detected 1.5- and 1.2-kb transcripts expressed at higher levels in heart, ovary, testis, liver, kidney, small intestine, and colon and at lower levels in spleen, prostate, brain, skeletal muscle, and pancreas. Expression was not detected in peripheral blood leukocytes, thymus, lung, and placenta. AIG1 expression is responsive to androgen. Northern blot analysis detected higher AIG1 expression in cultured dermal sheath cells following dihydrotestosterone stimulation.